The development of tomodensitometric devices, or tomodensitometers, is closely related to that of the measurements achieved by the X-ray source and the detection means rotatively driven about the patient with a view to gathering the information data necessary for the reconstruction of the image. Thus several successive "generations" of tomodensitometers have been developed. The first generation, called "translation rotation generation", has used an X-ray source emitting a narrow beam toward a single detector. The source and the detector have been integral with a translationally movable assembly supported by the rotative system. For each angular position the movable assembly would be displaced transversely with respect to the section to be imaged, so as to gather a bulk of measurement values, called "view". In such system all the rays which have passed through the section to be imaged are parallel, due to the structural characteristics of the device, for a given view. The second generation has retained the principle of translation, but has used an X-ray beam in the form of a slightly flaring fan and a multi-detector comprising a small number of juxtaposed detectors. As to the tomodensitometers of the third generation, which represent the major part of the devices produced up to now, these appliances use a fan-shaped X-ray beam having a larger flaring angle, and a multidetector comprising a great number of juxtaposed detectors adapted to receive all the rays that pass through the section concerned, for every angular position adopted during the measuring operation. Thus the translational displacement at each angular position is eliminated, whereby all the data necessary for the image reconstruction can be acquired within a substantially shorter time period.
The invention allows the spatial resolution of the reconstructed image to be improved in any one of the above-mentioned tomodensitometer types.